The present invention relates to hydraulic motors.
1. Field of the Invention
Hydraulic motors are well known for converting fluid energy into mechanical energy in a system. Hydraulic motors may comprise a number of different basic configurations but a widely used type of motor is one known as a gear motor. A gear motor uses a pair of intermeshing gear elements rotating within a housing. High pressure fluid delivered to an inlet induces rotation of the gear elements and causes a corresponding rotation of a shaft connected to one of the gear elements. Such motors are relatively inexpensive and are capable of handling relatively high pressures.
2. Summary of the Invention
To improve the efficiency of the motor, the end faces of the gear sets are sealed with a pressure compensating seal assembly in which the pressure of the fluid delivered to the inlet is applied to the seal to ensure close contact with the end faces. Whilst this arrangement improves the efficiency of the motor in use, it can lead to difficulties in initial starting of the motor. The high contact force provided by the pressure compensated seal inhibits rotation of the motor, particularly where the motor is connected to high inertia loads such as a cooling fan or mower reel.
3. Description of the Prior Art
It is accordingly an object of the present invention to provide a motor which the above disadvantages are obviated or mitigated.
In general terms, the present invention provides a gear type hydraulic motor in which pressure fluid is introduced in discrete areas between the gear faces and a pressure compensated seal to improve lubrication upon start up.
According therefore to the present invention there is provided a hydraulic motor comprising a housing having a fluid inlet, a fluid outlet and a cavity therebetween. A pair of intermeshing gear elements are rotatable in the housing about mutually parallel axes. Each of the gear elements have a set of gear teeth disposed about the periphery of the element and a support shaft extending from oppositely directed end faces of the set of gear teeth. A bearing assembly is located on opposite sides of the cavity in the housing to support the shafts for rotation about respective ones of the axes. Each of the bearing assemblies has a sealing face overlying the end faces and biased into engagement with the end faces by a pressure compensating seal located between the bearing and the housing. The sealing face has a channel extending partially about the shaft and a fluid communication with the inlet to introduce fluid under pressure between the faces.